1. Field of the Invention
This invention relates to a carrier substrate for producing a semiconductor device, a production process of the carrier substrate, a semiconductor device, and a production process of the semiconductor device. More particularly, this invention relates to a carrier substrate for producing appropriately a resin mold, to a lead-less surface package type semiconductor device, to a production process of the carrier substrate, to a semiconductor device, and to a production process of the semiconductor device.
2. Description of the Related Art
As the size of electronic appliances has been reduced and their integration density has become higher, in the field of semiconductor devices, the demand for the miniaturization of semiconductor chips per se and the reduction of a pitch of external connection terminals has become stronger so as to reduce the size of semiconductor devices and to increase their integration density.
As a structure for accomplishing a reduction in size of a resin mold type semiconductor device, Japanese Unexamined Patent Publication (Kokai) No. 9-162348 proposes a package structure of a lead-less surface package type.
As shown in FIG. 2(d) of the accompanying drawings, a semiconductor device utilizing this package structure includes a semiconductor chip 20, a resin package 22 for sealing the semiconductor chip 20, a resin protuberance 24 formed on the surface of the resin package 22 connected to a mother board in such a manner as to protrude from this surface, a plated film 14 applied to the outer surface of the resin protuberance 24 and a wire 30 for electrically connecting each electrode 28 of the semiconductor chip 20 to the plated film 14.
This semiconductor device is produced by utilizing a carrier substrate 50 for producing a semiconductor device, which substrate 50 includes a sheet-like metal substrate 12 which supports the plated film 14 and onto which the semiconductor chip 20 is mounted, as shown in FIG. 1(d).
First, a production process of the carrier substrate 50 will be explained with reference to FIGS. 1(a) to 1(d).
A resist 39 is first applied to both surfaces of the metal substrate 12. The resist on one surface 12a of the metal substrate 12 is then removed in the portion that corresponds to the resin protuberance 24 to form a resist pattern (FIG. 1(a)).
Next, the metal substrate 12 having the resist pattern formed thereon is immersed in an etchant solution, and etching is conducted until the portion of the metal substrate 12 that corresponds to the resin protuberance 24 is half-etched to form a recess 16 (FIG. 1(b)).
The resist pattern is left as such, and plating is applied so as to form the plated film 14 inside the recess 16 (FIG. 1(c)).
The resist is exfoliated to complete the carrier substrate 50 (FIG. 1(d)).
Next, a process of producing a semiconductor device utilizing the carrier substrate 50 so formed will be explained with reference to FIGS. 2(a) to 2(d).
The semiconductor chip 20 is fixed by applying an adhesive, for example, to one of the surfaces 12a of the carrier substrate 50 described above (FIG. 2(a)).
Each electrode 28 disposed on the semiconductor chip 20 and the plated film 14 formed on the metal substrate 12 of the carrier substrate 50 are electrically connected by a wire 30 through wire bonding (FIG. 2(b)).
A resin package 22 is formed by resin molding on the carrier substrate 50 in order to seal the semiconductor chip 20 and the connection portions by the wires 30 with resin (FIG. 2(c)).
The metal substrate 12 is removed by etching in such a fashion as to leave the plated film 14 of the carrier substrate 50 (FIG. 2(d)). In consequence, the plated film 14 is exposed to the outside of the package and functions as a connection surface of external connection terminals, and a semiconductor device having a structure capable of being connected to the mother board is completed. Incidentally, copper (Cu), for example, is used as the material of the metal substrate 12 so that etching can be conducted satisfactorily.
In the structure of the carrier substrate 50 according to the prior art described above, however, the plated film 14 that constitutes the external connection terminal adheres only to the resin that flows into the recess 16 along the shape of the recess 16 having a semi-spherical sectional shape. Therefore, adhering power is small, and the plated film 14 is likely to exfoliate from the surface of the resin protuberance 24 and invites the drop of reliability of the product.
Therefore, the problem that the reliability of the external connection terminal connected to the mother board of the semiconductor device cannot be improved remains unsolved.
It is therefore the object of the present invention to provide a carrier substrate that improves adhesion between a plated film that functions as an external connection terminal and the surface of a resin protuberance in a semiconductor device of a resin mold, lead-less surface package type and can improve reliability, a production process of the carrier substrate, a semiconductor device, and a production process of the semiconductor device.
To accomplish the object described above, the present invention provides a carrier substrate for use in the production of a semiconductor device including a semiconductor chip, a resin package sealing the semiconductor chip, a resin protuberance disposed on the surface of the resin package connected to a mother board, a plated film covering the surface of the resin protuberance and a wire electrically connecting an electrode of the semiconductor chip to the plated film, wherein the carrier substrate comprises a sheet-like metal substrate dissolvable by an etchant solution not dissolving the plated film, and suitable for fixing the semiconductor chip; a recess disposed at a position of the metal substrate corresponding to the resin protuberance, and having a bottom surface and/or side surface that are/is rugged; and a plated film covering continuously the bottom surface and the side surface of the recess, and having a surface shape corresponding to the surface shapes of the bottom surface and the side surface.
The present invention provides also a process of producing a carrier substrate for use in the production of a semiconductor device including a semiconductor chip, a resin package sealing the semiconductor chip, a resin protuberance disposed on the surface of the resin package connected to a mother board, a plated film covering the surface of the resin protuberance and a wire electrically connecting an electrode of the semiconductor chip to the plated film; the carrier substrate including a sheet-like metal substrate dissolvable by an etchant solution not dissolving the plated film, and suitable for fixing the semiconductor chip; a recess disposed at a position of the metal substrate corresponding to the resin protuberance, and having a bottom surface and/or side surface that are/is rugged; and a plated film for continuously covering the bottom surface and the side surface of the recess, and having a surface shape corresponding to surface shapes of the bottom surface and the side surface, the process comprising the steps of: forming the etching resist layer on both surfaces of the metal substrate; patterning the etching resist layer on one of the surfaces of the metal substrate to form a resist pattern having an opening at a position corresponding to the resin protuberance and a part of the etching resist layer remaining in an island-like shape inside the opening; etching the metal substrate, causing etching to proceed non-uniformly inside the opening due to the presence of the island-like etching resist layer, and thereby forming a recess having a side surface and a rugged bottom surface at the position of the opening of the resist pattern; and forming a plated film covering continuously the side surface and the bottom surface of the recess, and having a surface shape corresponding to the surface shapes of the side surface and the bottom surface.
In a preferred embodiment of the process of the present invention, the step of patterning the etching resist layer includes a step of forming the opening having a rugged periphery, and the step of etching the metal substrate includes a step of forming a recess having a rugged side surface corresponding to the profile of the opening and the rugged bottom surface. According to this embodiment, the surface area of the side surface of the recess can be increased, and adhesion with the sealing resin material can be further improved.
Preferably, the island-like etching resist layer has a rectangular frame-like shape. According to this embodiment, suitable ruggedness can be provided to the bottom surface of the recess, its surface area can be increased, and adhesion with the sealing resin can be further improved.
The present invention provides further a process of producing a carrier substrate for use in the production of a semiconductor device including a semiconductor chip, a resin package sealing the semiconductor chip, a resin protuberance disposed on the surface of the resin package connected to a motherboard, a plated film covering the surface of the resin protuberance and a wire electrically connecting an electrode of the semiconductor chip to the plated film; the carrier substrate including a sheet-like metal substrate dissolvable by an etchant solution not dissolving the plated film, and suitable for fixing the semiconductor chip; a recess disposed at a position of the metal substrate corresponding to the resin protuberance, and having a bottom surface and/or side surface that are/is rugged; and a plated film covering continuously the bottom surface and the side surface of the recess, and having a surface shape corresponding to surface shapes of the bottom surface and the side surface, the process comprising the steps of: forming an etching resist layer on both surfaces of the metal substrate; patterning the etching resist layer on one of the surfaces of the metal substrate to form an opening having a rugged profile at a position corresponding to the resin protuberance; etching the metal substrate to form a recess having a bottom surface and a rugged side surface corresponding to the profile of the opening at the position of the metal substrate corresponding to the opening of the resist pattern; and forming a plated film covering continuously the bottom surface and side surface of the recess, and having a surface shape corresponding to the surface shapes of the side surface and the bottom surface.
The present invention provides also a process of producing a semiconductor device including a semiconductor chip, a resin package sealing the semiconductor chip, a resin protuberance disposed on the surface of the resin package connected to a motherboard, a plated film covering the surface of the resin protuberance and a wire electrically connecting an electrode of the semiconductor chip to the plated film, the process comprising the steps of: preparing a carrier substrate including a sheet-like metal substrate dissolvable by an etchant solution not dissolving the plated film, and suitable for fixing the semiconductor chip; a recess disposed at a position of the metal substrate corresponding to the resin protuberance, and having a bottom surface and/or side surface that are/is rugged; and a plated film covering continuously the bottom surface and the side surface of the recess, and having a surface shape corresponding to surface shapes of the bottom surface and the side surface; fixing the semiconductor chip to the carrier substrate; electrically connecting the electrode of the semiconductor chip to the plated film of the recess of the carrier substrate by a wire through wire bonding; forming by resin molding a resin package for sealing the semiconductor chip and the wire on the carrier substrate, the resin package including the resin protuberance fitting to the recess of the metal substrate via the plated film and having a surface shape corresponding to the surface shape of the recess; and dissolving and removing the metal substrate while leaving the plated film covering the surface of the resin protuberance unremoved.
The present invention provides also a semiconductor device including a semiconductor chip, a resin package sealing the semiconductor chip, a resin protuberance disposed on the surface of the resin package connected to a motherboard, a plated film covering the surface of the resin protuberance and a wire electrically connecting an electrode of the semiconductor chip to the plated film, wherein the semiconductor device is produced by a process comprising the steps of: preparing a carrier substrate including a sheet-like metal substrate dissolvable by an etchant solution not dissolving the plated film, and suitable for fixing the semiconductor chip; a recess disposed at a position of the metal substrate corresponding to the resin protuberance, and having a bottom surface and/or side surface that are/is rugged; and a plated film covering continuously the bottom surface and the side surface of the recess, and having a surface shape corresponding to the surface shapes of the bottom surface and the side surface; fixing the semiconductor chip to the carrier substrate; connecting electrically the electrode of the semiconductor chip to the plated film of the recess of the carrier substrate by a wire through wire bonding; forming by resin molding a resin package for sealing the semiconductor chip and the wire on the carrier substrate, the resin package including the resin protuberance fitting to the recess of the metal substrate via the plated film, and having a surface shape corresponding to a surface shape of the recess; and dissolving and removing the metal substrate while leaving the plated film covering the surface of the resin protuberance unremoved.